1. Field of the Invention
The present invention relates to a roll photo film. More particularly, the present invention relates to a roll photo film in which a seal tape or fastening tape associated with a trailer can be used effectively without inconvenience for keeping a roll of the photo film wound tightly.
2. Description Related to the Prior Art
A Brownie photo film of the 120 type is known as a roll photo film in the field of photosensitive material, and includes a photo filmstrip, which is approximately 6 cm wide. Light-shielding backing paper is fitted on a back surface of the photo filmstrip, to be wound together about a spool in a form of a roll. A leader end of the backing paper is provided with a seal tape or fastening tape of paper, which adheres to the roll to keep it wound. When the roll photo film is used, at first a take-up spool is set in a photo film take-up chamber of a camera. The take-up spool is derived from a previously used roll photo film of which a previous photo filmstrip is removed, and of course has the same shape as the spool in the roll photo film newly to be used.
A photo film supply chamber of the camera is loaded with the roll photo film. Then the seal tape is removed from the backing paper, of which the leader end is inserted in a slit in the take-up spool in the photo film take-up chamber. The camera is manually operated for winding a portion of the backing paper about the spool by a predetermined amount. An arrow indicia printed on the surface of the backing paper becomes set at a start indicia positioned in the camera. Upon this, the winding operation is stopped. A back lid of the camera is closed. The roll photo film is wound further until a first frame set at an exposure aperture. A photo film counter indicates a numeral "1" representing setting of the first frame. Then the roll photo film is kept positioned without movement, to be ready for taking an exposure.
In the course of taking exposures, an exposed portion of the photo film with the backing paper is wound on the take-up spool in the photo film take-up chamber. After all the exposures are taken, the roll photo film is wound further. A trailer portion of the backing paper is disengaged from the spool in the photo film supply chamber before the entirety of the photo filmstrip and the backing paper is wound about the take-up spool in the photo film take-up chamber. Then the back lid of the camera is opened. A user manually takes the roll photo film out of the photo film take-up chamber while his or her fingers tightly holds the backing paper.
The roll photo film has another seal tape, of which one end is attached to a trailer end of the backing paper. A coating of adhesive agent is applied to the inside surface of a remaining end of the seal tape. The adhesive agent has such a characteristic that it is activated when moistened. A user moistens the seal tape with his or her tongue, and presses the seal tape against the backing paper, so that the roll of the roll photo film can be fastened without loosening the backing paper.
But it is likely that a certain photographer uses a great number of roll photo films. He or she must moisten the adhesive agent of the seal tape many times with his or her saliva, and is likely to feel ill as his or her tongue senses the adhesive agent. Also the use of the adhesive agent to be moistened by users is not acceptable in a sanitary point of view. Manufacturers shipping products should be responsible for preventing products from harming users, which is relevant to provisions of the recently enacted PL Law concerning responsibility for products. In such a situation, there is a suggestion in JP-U 5-47944 that release paper is used with the seal tape as a sticker, and that the seal tape is peeled from the release paper before being attached for the fastening.
The roll photo film disclosed in this document has a problem in that the seal tape is likely to stick to a photo film pressure plate of the camera particularly if the release paper is dropped away inside the camera. It is difficult to work this construction actually, because the release paper may drop during the photo film winding process in the course of the manufacture of the Brownie photo film. So JP-A 10-104803 (corresponding to Japanese Patent Application No. 8-260792) discloses an alternative structure in which the seal tape is kept bent in a channel shape.
The roll photo film disclosed in this publication also has a problem in that an adhesive surface of the seal tape is dropped away from the release layer when the seal tape passes through a photo film passageway in the camera. This problem occurs typically if the photo film passageway has a great curvature or is narrow.